In the process of manufacturing a semiconductor circuit element or liquid crystal display element, repeated patterns (wiring patterns and other line-and-space patterns) formed on the surface of the semiconductor wafer or liquid crystal substrate (hereinafter referred to generically as “the substrate”) are inspected for defects. In an automated surface inspecting apparatus, the substrate is placed on a tiltable stage, illuminating light (non-polarized light) for used in performing an inspection is irradiated onto the surface of the substrate, an image of the substrate is acquired based on diffracted light (e.g., 1st-order diffracted light) generated from the repeated pattern on the substrate, and the locations of defects in the repeated pattern are identified based on the differences between lightness and darkness (contrast) in the image (see, e.g., Patent Document 1). In such a surface inspecting apparatus, adjusting the tilt of the stage makes it possible to inspect for defects in a repeated pattern having a different repetition pitch on the substrate.
Techniques for inspecting a repeated pattern formed on the surface of a substrate include inspection using diffracted light such as described above (referred to hereinafter as diffraction inspection), using direct reflection light, utilizing changes in polarization state due to structural birefringence of the pattern (hereinafter referred to as PER inspection), and other techniques. These inspection methods enable resist application defects, line width defects based on defocusing or dose shift of an exposure apparatus, and other defects to be detected at high speed with high accuracy.
As the line width of the repeated pattern decreases, the wavelength of the illumination used for diffraction inspection must be shortened, and in repeated patterns having a line width of 45 nm or less, there is no illumination light source that is optimal for diffraction inspection, and the inspection is performed by PER inspection. In repeated patterns having a line width of 45 nm or less, changes in the shape of the pattern on the order of 1 nm must be detected, and high sensitivity is required to detect changes in the shape of the pattern.    Patent Document 1: Japanese Laid-open Patent Publication No. H10-232122